Yes, but what are we looking at? A full range speaker? A speaker + sub? If the former, then <50 Hz isn’t an issue.

My system has a typical 5.1 speakers. The front left/right can handle down to about 30Hz with no problem and then the crossover sends everything lower to my subwoofer.
Thanks for the info. But as Will noted, that doesn’t tell us what your graph is. Is it the main speaker(s) only, or both main and sub?


Regards,
Wayne A. Pflughaupt

Thanks for the info. But as Will noted, that doesn’t tell us what your graph is. Is it the main speaker(s) only, or both main and sub?


Regards,
Wayne A. Pflughaupt





As I recall, it was both front speakers. Checking the graph I see that the L+R button has been pushed, doesn't that indicate the signal was sent to both speakers?

My preamp crossover should activate the subwoofer automatically for any signal below 40Hz. If you wish, I can disconnect it and just use the front speakers. But as I mentioned, their frequency response really drops off around 29Hz.

I reconfigured my preamp to remove the subwoofer from the test.
This time the sound was coming from only the front L/R speakers.

Well, you have the usual peaks and depressions in the bass region. I’d move the crossover frequency up to 80-90 Hz and get a parametric EQ for your subwoofer. I wouldn’t do anything for the mains until you get an accurate reading with a calibrated mic.

Regards,
Wayne A. Pflughaupt

I just have one more graph to show you. I took a pair of scans, one with all crossovers set at 80Hz and the other with my standard settings (used for the other graphs).

Yellow = standard 40Hz
Orange = 80Hz crossover

Yellow looks a bit better…

Regards,
Wayne A. Pflughaupt

I'd like to get my Behringer ECM8000 calibrated. Any recommendations as to who can do a good job? Average or s.w.a.g. on cost? Anyone have experience with the calibrator noted in the TrueRTA help doc.?

Try this forum:
http://www.hometheatershack.com/forums/spl-meters-mics-calibration-sound-cards/

Or this lab:
http://www.cross-spectrum.com/

Kevin, good stuff! THX!

Xtrips,

I do not generally recommend input-only audio devices such as the icicle for use with TrueRTA because they lack audio output capability and thus are not useful for general audio testing.

That said, you can certainly use the icicle as an input device with TrueRTA. Just connect the icicle to the PC via a USB cable and select it as the input device in TrueRTA at the "Audio Device Selection" dialog box. Make sure to follow the Windows 7 specific Quick Start instructions. No other cables should be required.

Wayne commented:

<< I’m not as familiar with TrueRTA as I am another similar program, and perhaps John can correct me if I’m wrong here. But if TrueRTA requires or recommends a calibration file for the sound card, it might be difficult or impossible to accomplish that with something like the Icicle. The reason is that there is no line input and output that is needed to generate a calibration file.

So, unless you are certain the Icicle has flat frequency response from at least 20 Hz – 20 kHz, then your measurements will only be as accurate as the Icicle. >>


As an input-only audio device the icicle does not allow the use of TrueRTA's "Sound System Calibration" feature but you could still use a mic calibration file to correct the response of the mic itself. Hopefully the icicle preamp would have much less frequency coloration that the mic but keep in mind that this unit is designed for studio recording applications as opposed to measurement applications. Studio microphones and preamps are not normally "colorless". As Wayne says, measurements made using the icicle will only be as accurate as the icicle. This is true of all audio interface devices unless you go through the extra trouble to calibrate the test loop with the mic preamp included. Most often users calibrate the line-out to line-in loop. This calibration may not be exactly the same as the calibration for the line-out to mic-in test loop. This is just a fine point.

As an alternate you might consider the M-Audio "Mobile Pre" USB audio interface. It is powered from the USB bus and has mic preamps with phantom power. It also has line outputs.

Regards,

John

Hello

Thanks for the advises. I followed them all, almost.
Now I have a laptop running Win7 x64, an external Creative soundcard with stereo line in and out, a Behringer ECM8000 mike and its 802 pre-amp.
I also have a pair of RCA connectors for the loop.
I tried to use the guide at the beginning of this thread but from the very beginning the screens i get in TrueRTA don't match.
Isn't there a more up to date version of this guide somewhere?

Thanks

Ok. No answer. Let's try something else.
Does anybody here want to be my tutor?
I promise that I am very technical and that it won't be long.
I just want to get started.
Anyone?

I’ve never used RTA, but I have used another programthat's similar. Be happy to help if I can. What kind of trouble are you having?

Regards,
Wayne A. Pflughaupt

I've never used RTA, but I have used another programthat's similar. Be happy to help if I can. What kind of trouble are you having?

Regards,
Wayne A. Pflughaupt



Hi

Thanks. First what program do you use? I need to run acoustic measurements in different sites. I know and understand the theory of it all. I purchased the equipment so I am ready. But the manual is not really matching the screens I am getting. I'd be happy to accept your help.

I’ve used Room EQ Wizard. Why don’t you post us a picture of the graph(s) you’re not sure about? Is there an on-line manual for TrueRTA I could look at?

Regards,
Wayne A. Pflughaupt

Ok. No answer. Let's try something else.
Does anybody here want to be my tutor?
I promise that I am very technical and that it won't be long.
I just want to get started.
Anyone?

Xtrips,

I suggest you start with the "Self Test" as described in Application Note 1 of the online User's Guide.

What do you get with the initial sine wave test?

Regards,

John

I’ve used Room EQ Wizard. Why don’t you post us a picture of the graph(s) you’re not sure about? Is there an on-line manual for TrueRTA I could look at?

Regards,
Wayne A. Pflughaupt





Hello Wayne,

It's funny that you remind me of RoomEQ. It brings me back a few years earlier when i was using it with an old TagMcLaren av-32 pre-pro. Good'ol memories.
Anyway, i installed the new beta 5 and will try it this week-end.
I know where to find you if i need you.

Thank you

Xtrips,

I suggest you start with the "Self Test" as described in Application Note 1 of the online User's Guide.

What do you get with the initial sine wave test?

Regards,

John

Well, now i will sound like a complete newbie.
I started with the Self-test and that's where I didn't get what was expected in the first place.
I will post some graphs this week end.
Stand by.

Thx

<snip>
Is there an on-line manual for TrueRTA I could look at?

Regards,
Wayne A. Pflughaupt


Wayne,

The complete User's Guide is included in the free version of TrueRTA under the Help menu. Here is a link to the download page:

http://www.trueaudio.com/rta_down.htm

Cheers,
John

Thanks John. That’ll help me help these folks. http://www.hometheatershack.com/forums/images/smilies/t.gif

Regards,
Wayne A. Pflughaupt

Can anyone point me to a good (easy to understand) explanation to how to measure speaker frequency response using TrueRTA. I have been trying for some time now but cannot get measurement that makes sense.
The attached screen shot is typical of what I get when I do a "Quick Qweep" of any driver. The driver in this case is a Saba 8" Mid. I have been through the TrueRTA site & found nothing specifically about measuring speaker response, I have also scoured the web, to no avail.

Oh, I am challanged when it comes to instruction, which doesnt help, for me a picture tell a thousand stories.

Or maybe somebody can tell me what I might be doing wrong?

I am using a ECM8000 mic with a calibration file, plugged in to a Behringer preamp, looped back through the Realtek HD Audio soundcard in my Dell PC. I have calibrated the soundcard.

I am thinking of buying a M-Audio PreMobile. Is that a good idea?

David

Hello TrueRTA users! This is to announce that TrueRTA version 3.5.0 has been released and is available for download at trueaudio.com. This is a free upgrade for all TrueRTA version 3 users. Here is a link to the download page:
The new version is Windows 7 compatible and allows selection of audio devices from within the software. Quick Sweep now operates reliably at all signal levels. Many small improvements and bug fixes have been made. An all new Quick Start section details setup under Windows XP and earlier, Vista and Windows 7. Application Note 1 covering self test of the PC sound system has been greatly expanded and should now answer many of your original questions and get new users started using the software more quickly. I hope you find the new version easier to use than ever and that it allows you to be more productive in your audio testing.

Thank you for using and supporting TrueRTA!

Warm Regards,

John

When I go to the link you posted for the user 3 upgrade I cannot find where to download it? am I blind?

Can anyone point me to a good (easy to understand) explanation to how to measure speaker frequency response using TrueRTA. I assume you reviewed the opening pages of this thread?


I am thinking of buying a M-Audio PreMobile. Is that a good idea? It won’t do anything for you that your Behringer and Realtek aren’t already doing.

Regards,
Wayne A. Pflughaupt

I assume you reviewed the opening pages of this thread?


It won’t do anything for you that your Behringer and Realtek aren’t already doing.

Regards,
Wayne A. Pflughaupt



Yes I have read the start of this thread. I have read lots & lots, but no matter what I do the measurements are always like the one I posted.

I have also down loaded HOLMImpulse & tried it & am having similar problems, no matter what I do I dont get proper measurements.

There are two reasons for the M-Audio preamp, I get to see if it is my sound card causing problems & two I can use it with my daughters laptop, which is much more convenient. I am also going to buy a new EMC8000, I bought the one I have second hand on Ebay, I'm trying to eliminate any hardware issues.

Of course the real problem could be hardware I can't replace, my brain.

Any help would be most welcome.

David

I had my ECM8k calibrated by Herb Singleton @ Cross Spectrum. Very satisfied with the quick service and returned documentation. Along with the paper and emailed graph results, Herb sent data files for the 3 (0,45,90 degree) response results. These are files of file type FRD (i.e. narrow_band_response__0_degree.FRD) that "mostly" look like a mic cal file (frequency <space> response) that I expected to see but have an additional zero on each line. Also, they are not directly readable (i.e. flat text) via Notepad. I can read them via Word, Wordpad, and another text editor. My question is, can I change the file type from FRD to TXT and expect my RTA program (TrueRTA) to properly read them as-is with the trailing zero on each line? I can certainly edit all that out and rename the files. But I was curious as to the file format, content, etc, that he supplied. I'm concerned because I don't know of a way to confirm that the mic cal file is being correctly interpreted (ignoring the trailing zero) if I just change the ftype from FRD to TXT and load it.

Well it turns out the ECM8000 microphone some kind soul sold me on ebay was a dud. I bought a new one & have been getting measurements that make sense.

It's nice to know my brain wasn't the problem after all:D Now the fun begins

Im thinking of buying the following for my test rig:

- E-mu 0404 (USB)
- ECM8000 (calibrated)
- TrueRTA

Can I connect the 0404 directly to a speaker or do I need an amplifier also?
If an amplifier is needed, then won't the amplifiers frequency response affect my measurements?
Im very new to this game, so correct me if im wrong here.

If your speakers are active (self-powered), then you don't need a separate amplifier. If they aren’t, then you will need an amp.

Typically an amplifier has virtually flat frequency response, so you don’t need to worry about it affecting your measurements.

Regards,
Wayne A. Pflughaupt

I want to measure dB SPL as a function of time not frequency. Is there any way doing this with the true rta software?

To do a proper spl calibration, would I need a spl meter? I'm trying to get set up using a Dayton EMM-6 measurement mic with calibration file and a M-Audio Profire 610 I will use as a soundcard.

It should be fine. You’d just have to keep in mind that the SPL (dB) side of the graph isn’t meaningful in an absolute sense. However, you would still be able to determine that you have a 8 dB peak at a certain frequency, for instance.

Regards,
Wayne A. Pflughaupt

I had my ECM8k calibrated by Herb Singleton @ Cross Spectrum. Very satisfied with the quick service and returned documentation. Along with the paper and emailed graph results, Herb sent data files for the 3 (0,45,90 degree) response results. These are files of file type FRD (i.e. narrow_band_response__0_degree.FRD) that "mostly" look like a mic cal file (frequency <space> response) that I expected to see but have an additional zero on each line. Also, they are not directly readable (i.e. flat text) via Notepad. I can read them via Word, Wordpad, and another text editor. My question is, can I change the file type from FRD to TXT and expect my RTA program (TrueRTA) to properly read them as-is with the trailing zero on each line? I can certainly edit all that out and rename the files. But I was curious as to the file format, content, etc, that he supplied. I'm concerned because I don't know of a way to confirm that the mic cal file is being correctly interpreted (ignoring the trailing zero) if I just change the ftype from FRD to TXT and load it.

Im running TrueRTA on Windows 7 64-bit, and if i try to load the file after changing it from .frd to .txt, the program closes with an error :confused:

edit:
Found the answer, too many data points in the file. (1600+, and the limit for TrueRTA is a little over 800)

In the instructions for measuring the Line In and Line Out voltages they say to use a loop to in and out and a Y adapter from which to take the voltage measurements. If the same loop is in place for both voltage measurements (Input & Output) what's the purpose of measuring at the input and again separately at the output? If the In and Out are connected together each test would produce the same voltage level. Or am I missing something here (entirely and probably possible)?

Stumped... :confused:

P.S. Where did the rest of this thread go? It appears to end in November 2010.

subscribe

In the instructions for measuring the Line In and Line Out voltages they say to use a loop to in and out and a Y adapter from which to take the voltage measurements. If the same loop is in place for both voltage measurements (Input & Output) what's the purpose of measuring at the input and again separately at the output? If the In and Out are connected together each test would produce the same voltage level. Or am I missing something here (entirely and probably possible)? The purpose of the loopback is for the program to determine the frequency response of the sound card, since many of them are not perfectly flat. The program can then make corrections to any measurements to compensate for the sound card.

P.S. Where did the rest of this thread go? It appears to end in November 2010.
It didn’t end; there just haven’t been any new posts since then.

Regards,
Wayne A. Pflughaupt

Hi Wayne,

Thanks for the quick reply. I think we're talking about two different things. I think you're describing the purpose of the "Sound System Calibration" menu item. That one I understand. What I was referring to was the "Input Calibration" and "Output Calibration" menu items where you measure the voltage of the test signal. If during those tests the same loopback and Y connector is still in place (for each test) I don't understand why it's necessary to do an Input AND Output Calibration. Because essentially you're still measuring the same connection twice.

Hi,

Thanks for all your information so far. I have a question.

I've got a Mackie Onyx Blackjack interface which in normal use runs at 44 kHz. I've read the instructions for soundcard calibration that says to do that with I/O settings at 48 kHz.

Should I better make the calibration file at 44 or at 48 kHz settings due to the above?

Kind regards, Charles

Good evening all,

Newbie with true RTA, read the dummie guide, purchased the 1/6 octave, followed the guide for setup calibration and measurement and you can see in attachment what i got. Not sure what to make of it so i am seeking your input

Alain

Is it possible to use TRTA while playing a CD of pink noise?

My car's sound system has some obvious FR flaws that are not correctable using its EQ adjustments. I am considering burning CDs that have been processed with an EQ correction curve derived from direct measurement of the system's FR. There is no easy way for me to feed the pink noise from TRTA into the system in real time, so is it possible to use it with pink noise on a CD?

DEAD THREAD ALERT! DEAD THREAD ALERT!!

I had my system professionally voiced only 20 years ago, and it's already giving me problems!!

Of course, I've changed a lot of components ... and I've moved since. Think that has anything to do with it? :rolleyes:

So, here I am. Got the 1/6 octave version, but mostly for the additional calibration features. I expect I'll be running it at 1/3 mostly for home audio analysis. Also went with the TRTA website "system two" equipment list in hopes of heading off any incompatibility issues. Keeping my fingers crossed that XP Tablet Edition doesn't throw in any unexpected roadblocks. That's what came loaded on my Fujitsu Lifebook. Haven't seen anything in the thread one way or another on that OS.

Wish me luck!

Oh. I figured my trusty old BSR 14 octave equalizer would come up short, so I went wandering thru eBay and scored a Yamaha Q2031 (2 channel 1/3 octave) for $85 including shipping. That's about 10 cents on the dollar from the original purchase price, so it's either a steal or a brick - can't wait to find out. Add another $10 for a set of phone plug to rca adapters and I should be good to go. I've heard tell that a picture is worth a thousand words ... I do like the idea of having the 1/3 octave results on the TRTA screen directly correspond to the sliders on the eq.

Oh. I figured my trusty old BSR 14 octave equalizer would come up short, so I went wandering thru eBay and scored a Yamaha Q2031 (2 channel 1/3 octave) for $85 including shipping. That's about 10 cents on the dollar from the original purchase price, so it's either a steal or a brick - can't wait to find out.It’s a brick. At least for pro-audio applications it is. Its filters are overly broad, so it’s not terribly useful for feedback control, but that same “problem” probably makes it better suited for “sound shaping” in home audio. The later models (“A” or “B” suffix, IIR) are reasonably quiet and only slightly colored (you’ll probably only notice the difference by switching back and forth between “engaged” and “bypass” using a pink noise signal source). However, if you’re getting one of the older models with the +4 and -20 dB rear-panel switches, it may be noisy if you have to use the +4 position.

For full range use, a better choice would have been the digital YDP-2006 parametric or YDG-2030 1/3-octave models, which have pristine sonics. They can usually be had on ebay in the $100-$150 range.

Regards,
Wayne A. Pflughaupt

Dang ... five minutes of intensive research down the drain ... <G>

Either way, should still be a major improvement over what I had, and I only plan to use it for my home system anyway, so I guess I stumbled into something decent. AssUming it doesn't burst into flames when I plug it in. It is the "B" series, so I suppose I could have done worse. I flipped a coin as to whether to use the XLR or phone jack inputs - either way, I'd need RCA adapters. I went with the phone jacks mostly because the adapters were cheaper ... and the rest of the system is unbalanced so why complicate things? Feel free to tell me I screwed up there too.

** Sounds like you're familiar with the eq - any idea how old the thing is? I see they're still selling the same series new, but that doesn't mean much. Anything older than maybe 10 years and I'd probably want to do a full recap on the board and power supply just to be able to experience the thing in all its ... mundane glory. At the very least, I expect some DeOxit on the sliders would pay dividends.

___________________________

I got the Dayton mike in the mail today ... spent the next half hour doing a shell game hunt for the configuration file on their website. I finally snuck in thru the back door using the link Parts Express has on their site. Here it is in case anyone else has the same problems finding it:

http://www.daytonaudio.com/support-Emm.cfm

___________________________

Oh. Speaking of parametric. I've got a McIntosh MQ104 to take care of the big lumps. I figure to run a curve without any processing, use the MQ104 to clean up the big spikes, then run another curve with that in line to see what's left for the Yamaha to deal with. In regards to the digital memory machines like the YDG-2030 you mentioned, one of things that I like about the Q2031 is the old skool sliders. I've got three "smart" eqs collecting dust on the bench that have gone south on me. Either they can't remember anything, or they make it up as they go along, throwing random settings every time I fire them up. My BSR14/14R is crapping at random again, which is what got me thinking eq again in the first place.

Help out a dummy here. Is there an advantage to insertion of all these processing components into the audio stream IF one has an AVR with Audyssey? Or is it Just a hobbyist "thing "??

Help out a dummy here. Is there an advantage to insertion of all these processing components into the audio stream IF one has an AVR with Audyssey? Or is it Just a hobbyist "thing "??

I'm a dummy too, but I recently stayed at a Holiday Inn Express. No, really, I recently bought most of the equipment listed here, but haven't used it yet.

I suppose one could call it a hobbyist thing, but I get the impression that using a professional mic and a sound card, a pink noise generator, and professional software such as that mentioned here yields more precise, accurate, and comprehensive measurements. Furthermore, they allow a human, not a software algorithm -- albeit a very sophisticated one -- to address the deficiencies in the room. Even with an AVR with Audyssey, a hobbyist could get all these measurements and feedback and manually correct many of the things Audyssey missed or wasn't so accurate in addressing.

That's my take, anyway, for what it's worth. YMMV.

If people want to know the truth about any piece of equipment, any change in their system, any placebo effect. They need to have measurement equipment/software


IMO, the Dayton Omni measurement system is probably what you guys should buy if they want a complete package. Its superior to anything TrueRTA is offering.


FWIW, TrueRTA is simply a waste of $$$ since ARTA, REW and HOLM are free and easier to use.

FWIW, TrueRTA is simply a waste of $$$ since ARTA, REW and HOLM are free and easier to use.

Lol. Yeah, after looking around a while, I finally figured out that REW is free and does just about everything the software packages that aren't free do. I installed it and the only thing stopping me from jumping in is the learning curve associated with any new kind of software and technical task.

The only equipment I had to buy that I didn't already have is the Behringer condenser mic (had cardioid mics and a Radio Shack SPL meter, but didn't want to use those) and XLR to USB and phantom power source converter. Already had a nice external sound card for use with my netbook.

Apart from the learning, I'm good to go with REW.

I flipped a coin as to whether to use the XLR or phone jack inputs - either way, I'd need RCA adapters. I went with the phone jacks mostly because the adapters were cheaper ... and the rest of the system is unbalanced so why complicate things? Feel free to tell me I screwed up there too. Nah, 1/4” plugs are just fine. As a “freebie” side benefit though, if you have downstream amps with balanced inputs you’d have balanced outputs from the EQ, despite using an unbalanced input signal.

** Sounds like you're familiar with the eq - any idea how old the thing is?Not sure about the B-version specifically, but the Q series has been around since at least the early ‘90s, and the A-version since the late 90s. Can’t confirm it, but I‘ve heard rumours that it’s sourced from Phonic. :(


In regards to the digital memory machines like the YDG-2030 you mentioned, one of things that I like about the Q2031 is the old skool sliders. I've got three "smart" eqs collecting dust on the bench that have gone south on me. Either they can't remember anything, or they make it up as they go along, throwing random settings every time I fire them up. My BSR14/14R is crapping at random again, which is what got me thinking eq again in the first place. With all due respect to the vintage BSR, you’re comparing it to a $2000 professional equalizer. Having used several YDP-2006’s (the parametric cousin of the YDG-2030), the only ones I've had problems with had lived a hard life on the road.

That said, there’s no denying the “cool” mystique of a gaggle of sliders... :)

Regards,
Wayne A. Pflughaupt

Help out a dummy here. Is there an advantage to insertion of all these processing components into the audio stream IF one has an AVR with Audyssey? Or is it Just a hobbyist "thing "??For starters, not everyone has Audyssey. And some versions of Audyssey are not as powerful or effective as others. No auto-EQ system gets perfect results in every room, every time. There’s no substitute for the ear. Personally I wouldn’t buy a receiver with Audssey or any other auto EQ system that didn’t offer the capability to manually tweak the adjustments. If you have that capability on tap, then there’s no reason to use an outboard EQ.

Regards,
Wayne A. Pflughaupt

IT'S ALIVE! IT'S ALIVE!!!!

I just like waking up dead threads. <G>

That said, there’s no denying the “cool” mystique of a gaggle of sliders...

Not to take away from the uber kewl mind candy of a ginormous flourescent display on yet another of my old BSRs. I've got an 4000XR that I'll probably hook up passive just for the real time display while I'm listening to music. It's a good unit, but only 12 band, so it tends to fall woefully short when trying to voice a "challenged" room. I've also got a BSR spacial enhancer that does that neat "bloom from the middle" flourescent display - also running passive. Goes nice with the 600 watts of photo floods and chauvet led bars. Ya ... I like lights.

As to what does what better, audio is in the ear of the beholder. I like the idea of an auto tune capability, and really ... TRTA is just that ... other than it requires me to manually transfer the curve to the eq. Being able to tweak the IO for an accurate baseline is a definite plus, and I really like the option to add a "room curve". And yes, there is apparently a bit of a learning curve also, but that's part of the fun. Even then, I expect what is sonically PERFECT will fall short in the real world. My version of it anyway.

PS - in my version, post processing is almost an obsession. Audio purists tend to cring in horror and reach for their talismans against evil when they see what I'm running here ... I seldom listen to anything as the artist originally intended, and consider that a good thing. What's a bit of DBX, EQ, SQ, QS, pro logic, sonic holography and sub synth amongst friends??

http://brainfartz.com/images/Stereo%20Stuff/QRX-Home-System.jpg

if you have downstream amps with balanced inputs you’d have balanced outputs from the EQ, despite using an unbalanced input signal

I'm completely imbalanced here, but I expect you've figured that out by now ... <G>

This question may of been answered already, but I haven't seen it in a very clear manner, so I'm sorry if this is a repeat.

I have an Audix TM1, so I know my mic's response is very flat. I want to use this to EQ a room, but I wish to use the existing equipment's pink noise, instead of the noise from TrueRTA. I did some quick tests, and it seems to be reading levels much lower than it should. (Low SPL's for sounds that I know are much higher.)

I know the system calibration method, where you loop line in and line out, but that is only if you're going to be using TrueRTA's noise, correct?

How do I calibrate correct SPL if I'm only using the line in, and external pink noise? (I don't own an actual SPL meter right now, so I can't go that route, besides an app on my phone.)

Thanks!!

This question may of been answered already, but I haven't seen it in a very clear manner, so I'm sorry if this is a repeat.

I have an Audix TM1, so I know my mic's response is very flat. I want to use this to EQ a room, but I wish to use the existing equipment's pink noise, instead of the noise from TrueRTA. I did some quick tests, and it seems to be reading levels much lower than it should. (Low SPL's for sounds that I know are much higher.)

I know the system calibration method, where you loop line in and line out, but that is only if you're going to be using TrueRTA's noise, correct?

How do I calibrate correct SPL if I'm only using the line in, and external pink noise? (I don't own an actual SPL meter right now, so I can't go that route, besides an app on my phone.)

Thanks!!

Tuirn up the gain on the microphone?

This question may of been answered already, but I haven't seen it in a very clear manner, so I'm sorry if this is a repeat.

I have an Audix TM1, so I know my mic's response is very flat. I want to use this to EQ a room, but I wish to use the existing equipment's pink noise, instead of the noise from TrueRTA. I did some quick tests, and it seems to be reading levels much lower than it should. (Low SPL's for sounds that I know are much higher.)

I know the system calibration method, where you loop line in and line out, but that is only if you're going to be using TrueRTA's noise, correct?

How do I calibrate correct SPL if I'm only using the line in, and external pink noise? (I don't own an actual SPL meter right now, so I can't go that route, besides an app on my phone.)

Thanks!!



TrueRTA requires that you calibrate the on screen SPL readings. You use the SPL Calibration function. If you don't own an SPL meter, then you have no reference for the SPL calibration.

Note that you must recalibrate SPL any time you make a change in gain in your microphone to PC audio chain.

You don't need accurate SPL numbers to EQ, so don't let that stop you from doing whatever you are going to do.

Thank you for the reply! One more quick question: if I am not using RTA's noise (so I am not using any output audio from the laptop) is it better for me to not use system calibration , since that takes into account the sound card's output as well?

Thanks again!!

Thank you for the reply! One more quick question: if I am not using RTA's noise (so I am not using any output audio from the laptop) is it better for me to not use system calibration , since that takes into account the sound card's output as well?

Thanks again!!


You have to use the soundcard calibration file to make the TrueRTA FR curves flat.

The output and input calibration is similar to the SPL calibration. You only need to calibrate output and input levels if you need accurate dBu numbers.

Just as a note, I calibrate everything when and as needed. I also use a home made CD for my test soundtracks so I don't have to connect anything to my receiver.

I have an Audix TM1, so I know my mic's response is very flat. I want to use this to EQ a room, but I wish to use the existing equipment's pink noise, instead of the noise from TrueRTA. I did some quick tests, and it seems to be reading levels much lower than it should. (Low SPL's for sounds that I know are much higher.) I don't see any mention there of a mic pre-amp. That mic requires a pre-amp and phantom power.

Regards,
Wayne A. Pflughaupt

My laptop has a "Mic" input and not a line in. I was only using a phantom power box and then directly into my Mic port, using an XLR -> minijack cable. Seemed to be receiving audio just fine, but only with incorrect SPL, mentioned earlier.

It's my understanding that if it's a Mic input jack, that has a preamp?

Correct, but if it doesn’t have a gain control that would account for your SPL issue. Also, I wouldn’t expect a computer’s mic input to be terribly accurate, and it can’t be calibrated. Keep in mind that your measurement accuracy will be no better than the weakest link in the signal chain. I expect you’d get better results with a legitimate pre-amp like the Behringer XENYX 502 or a combo USB audio interface/pre-amp like the M-Audio Mobile Pre or TASCAM US122 (to name a couple, there are plenty of similar products on the market). I mean, you’ve invested in a rather pricey mic for this, so it seems counter-productive to “cheap out” by using the computer mic input.

Regards,
Wayne A. Pflughaupt

Thank you for the recommendation!! I like that the USB interface devices function as both a pre-amp and providing phantom power... for a really good price at that. I looked at both and I am leaning toward the M-AUDIO, is there any you'd recommend over another (cleanest audio?), or are they all pretty decent?

Also, just to be clear (sorry to be repetetive)... even though I won't be using any test tones from TrueRTA, it is still a good idea to do a system calibration? (Looping the line out into my input.) I thought I read somewhere that if I'm not using the tones from TrueRTA, doing that calibration can skew the numbers, since it's taking into account my computer's audio output. Is that at all true?

I looked at both and I am leaning toward the M-AUDIO, is there any you'd recommend over another (cleanest audio?), or are they all pretty decent? I’ve only used the TASCAM myself, so I can’t say. However, ”clean” isn’t really an issue for taking room measurements. It’s only relevant if you intend to use the interface for its intended purpose: Recording. If that’s the case, you should have no problem finding on-line user reviews to make that determination. That said, I think most of these things have amazingly flat response. For example, the US122, is down only 1/4 dB or so at 20 Hz, IIR. Technically it doesn’t even need a calibration file!

BTW - separate from that you should Google for some reviews to make sure any interface you’re interested in is compatible with your operating system. This post (http://www.hometheatershack.com/forums/rew-forum/28299-first-time-rew-plot-2.html#post262011) will give you some pointers in what to look for in the reviews.


Also, just to be clear (sorry to be repetetive)... even though I won't be using any test tones from TrueRTA, it is still a good idea to do a system calibration? (Looping the line out into my input.) I thought I read somewhere that if I'm not using the tones from TrueRTA, doing that calibration can skew the numbers, since it's taking into account my computer's audio output. Is that at all true? I don’t know a lot about the specifics of TruRTA, but I doubt the system calibration has anything to do with the test signals it generates. The purpose of the system calibration is to eliminate any inaccuracies in response that the sound card and mic have. It would be silly for the compensation to be built-in to the test signals. If that were the case, TruRTA would have to specify that the system could only be used with an XYZ sound card and ABC mic, would it not? Because using any others would render the system inaccurate.

With sound card and mic calibrations in place, any reliable test signal can be used. For instance, I’ve used the pink noise signal from my hardware AudioControl RTA to take measurements with a software program similar to TruRTA, and it works fine.

Hope that helps.

Regards,
Wayne A. Pflughaupt

Sorry I was a bit unclear with the question. Since I won't be using my sound card's audio output for these tests, but instead the pink noise built into the hardware I'm testing, would running the system calibration unnecessarily take into account imperfections in the sound card's output, which shouldn't be a part of the calculations, since it's not being used?

Correct, but if it doesn’t have a gain control that would account for your SPL issue. Also, I wouldn’t expect a computer’s mic input to be terribly accurate, and it can’t be calibrated. Keep in mind that your measurement accuracy will be no better than the weakest link in the signal chain. I expect you’d get better results with a legitimate pre-amp like the Behringer XENYX 502


I have a Xenyx 502 that is available for a good price (I ended up going in a different direction). PM me if you are interested

Sorry I was a bit unclear with the question. Since I won't be using my sound card's audio output for these tests, but instead the pink noise built into the hardware I'm testing, would running the system calibration unnecessarily take into account imperfections in the sound card's output, which shouldn't be a part of the calculations, since it's not being used?Even if you don’t use the soundcard’s output for generating test signals, the output circuitry is still being used to send the signal from the mic to the computer: E.g., mic -> mic pre-amp - > audio circuitry (gain stages, etc.) –> USB –> computer. So yes you still need the calibration file for the sound card.

But like I said, you may find that the response of the combo audio interface you choose is so good that it doesn’t need a calibration file.

Regards,
Wayne A. Pflughaupt

Cool, thanks again for all the info.

So here's an interesting tidbit... if I run the calibration from the line out to mic in (no USB device involved)... the original EQ line is actually quite straight, and very close to being perfect. When I involve the M-Audio MobilePre in the calibration (line out -> XLR-in on MobilePre -> USB input), the original EQ line has a lot more variances (dips and spikes)... which is then corrected of course by the end of the calibration.

Correct me if I'm wrong, but this tells me that my existing sound card has some very flat response to begin with, which means that it isn't improperly coloring the EQ of the MobilePre much, if at all?

This question is probably better directed to Digidesign or the makers of my OS/laptop (MS & Dell), but I thought I'd throw it out there in case anyone's run across it.

Because I'm running XP, the guys at the local pro audio shop gave me a deal on an old Mbox1 that I'm trying to use as the pre/phantom for my dbx RTA-M mic. They installed the drivers for the mbox, along with a copy of Protools LE (vers 7.4). I'm seeing audio signal into protools, but not in the TrueRTA.

I'm pretty sure it's related to the following: on TrueAudio's FAQ page, under "Sound Card Questions", the first paragraph of the response to the first question has directions to tell Windows that I'm using an external sound system, by opening the "sounds and audio" control panel and clicking on the audio tab. While I can select the Mbox as the default playback device, it doesn't give me the option to select it as the recording device. The only option is the installed card ("Sigma Tel Audio").

This is my first foray into Protools (I'm mostly a live-sound guy) but my understanding is that this version (and therefore the Mbox?) won't work with post-XP OS's. My laptop does tend to be a bit "buggy" and obviously both it an the OS are pretty old. Still, it'd help me out quite a bit to get it running. Any help is appreciated.

Hello All,

I read Brent Butterworth article in S&V for DIY audio measurement and it has me interested in trying this. In Brent’s article it seems a mic preamp was not necessary when using laptops internal sound card. From reading this thread it seems many recommend the preamp. Also it seems the EMM-6 mic has a built in preamp, how does this differ from the external preamp? If someone could elaborate further I would be grateful.

Thanks Bob

Mics require an external pre-amp; they don’t have built-in pre amps. If you’re using the Dayton EMM-6 or Behringer ECM 8000, they require phantom power, so a computer pre-amp won’t work.

Regards,
Wayne A. Pflughaupt

What is the differnece between the M-Audio Mobile Pre USB and something like the Rolls MP13 Mini-Mic Preamp with Phantom Power? thanks for the help, Bob

The Mobile-Pre (and similar units) combine the mic pre-amp, phantom power and USB interface in a single package. With the Rolls you’d still need an additional USB sound card.

Regards,
Wayne A. Pflughaupt

Brent’s article suggested the mic had a preamp, I knew it I read it somewhere. Must have been a misprint.
“The EMM-6 and ECM-8000 require phantom power: a separate DC supply that sends voltage up the cable to power the mike’s internal preamp.”
http://www.soundandvisionmag.com/article/how-diy-audio-measurement?page=0,2

>With the Rolls you’d still need an additional USB sound card.<
Unless you try to use the sound card in your laptop?

So I think I have it, Windows Laptop, EMM-6 , TrueRTA(1/6), M-Audio Mobile Pre and connecting cables. Laptop aside the price for those componets are pretty close to the complete Dayton OmniMic Package which I imagine is another alternative.

Thanks Bob

Some mic types such as ribbon and electrets do have built-in pre amps, but condenser mics (such as the EMM-6 and ECM-8000) do not.

Regards,
Wayne A. Pflughaupt

Hi,

I hope you can help me out with this one:

I bought a new laptop and reinstalled TrueRTA on this one, but the mic signal is not being read. I've calibrated the soundcard and activated the (advised) mic calibration file for the Behringer ECM8000.

The mic works; I've tested it in other software with the same soundcard, so I'm a bit flabbergasted right now.

Please let me know if this sounds familiar and you know a solution.

Regards,

Charles

Solved it. Had to manually adress it in the Audio Device selection.

I'm trying to figure out if I can use equipment I already have to perform a RTA measurement. I have a Tritton AX 720 headphone that comes with a processor. One of the things this processor can do is act as a USB microphone to a PC. It has it's own power supply. I already have a radioshack SPL meter. Should this processor work with a laptop to perform the RTA measurement?

Here is a link that explains the unit in more detail.

http://www.jeffsreviews.com/Articles/comp%20hard%20mar09-/tritton%20ax%20720/ax%20720.html

Hi guys,

I'm new to the forum. I've read all the posting here and I don't see anything regarding headphones.

I'm trying to set up a headphone tester at my home. At the lab, my guys use Clio, anechoic chambers, HATS and IEC711 mics. But that's just not in my budget. I'm looking to build a test jig so I can approximate and make some mods to headphones to tweak freq responses.

I can make the adapters to house the mic and couple to the IEM's and headphones etc. but I'm curious if anyone here has successfully been able to use TrueRTA with MobilePre/ECM8000 for this use.

Or if anyone has suggestions on what I might be able to source for a little DIY project, I'd greatly appreciate it!

Well, I spent the weekend researching and it seems there's no real workaround. I might have to pluck down $800 for a IEC 711 microphone if I want realistic FRs. :(

I'm curious if anyone here has successfully been able to use TrueRTA with MobilePre/ECM8000 for this use.
If you already have ECM8000, put it next to the headphone (block the other side so it won't interfere) and see if it works.

Hi all,
First post in this forum, sure to not be the last. At the beginning of this thread there were some non-functional links to pictures of the proper wiring connections for Mobile Pro,(I think), for use with TruRTA. I am assuming these would be the same for the Tascam 122 that I will be using. Can anyone provide a working link? If not, a step by step explanation would be greatly appreciated. Please bear in mind that I am the epitome of those in need of the "Dummies" series of texts!:D

TIA,
Jim

This picture is for a different measurement platform, but the cabling / connections should be the same.

REW cabling basics (http://www.hometheatershack.com/forums/attachments/spl-meters-mics-calibration-sound-cards/17473d1259255428-rew-cabling-connection-basics-rew-connection-usb-soundcard.jpg)


Regards,
Wayne A. Pflughaupt

That is perefect Wayne! Thank you!!
Jim

I got my M-Audio Mobile Pro (Generation 1) and trying to set it up on my lapto running Windows 7 Home Premiium 64bit and having a very strange behaviour.

Without anything connected to in or out , no mic no wire, nothing, just a usb cable, all gain controls on sound card are turned down to zero.

Now when I start the analyzer in TrueRTA I see a very high noise up to 70db, I will try to post the image.


Has anyone seen such behaviour? I did a calibration and that does not affect it? I have another PC (WIn 7 Ultimate 32 bit) with Audiotrak 7.1 HIFI PCI sound card and when I loop that card I can hardly see any noise there and it is below0 db when nothing is connected.

still trying with image

coming soon

Ok , here is the image. Sorry it took so long :O


http://imageshack.us/photo/my-images/718/truerta.jpg/

Can you explain additionally how to calibrate computor and room background noise in TrueRTA?

And what is apsolute SPL?

Thanks!